Electronic and Optical Properties of CsGeX 3 (X= Cl, Br, and I) Compounds.

We used first-principles calculations to investigate the electrical and optical properties of CsGeX 3 (X = Cl, Br, and I) compounds. These materials present rich and unique physical and chemical phenomena, such as the optimal geometric structure, the electronic band structure, the charge density distribution, and the special van Hove singularities in the electronic density of states. The optical properties cover a slight red shift of the optical gap, corresponding to weak electron-hole interactions, strong absorption coefficients, and weak reflectance spectra. The presented theoretical framework will provide a full understanding of the various phenomena and promising applications for solar cells and other electro-optic materials.